RESUMO
To evaluate the effect of the physical properties of density and viscosity on airway resistance, three perfluorochemical fluids (PFCs) were used: FC-75, Liquivent, and APF-140. Using two different endotracheal tubes (ETT) (3.0mm ID and 4.0mm internal diameter (ID)), the three fluids were studied at steady state flow conditions over a range that approximated peak flow required for liquid ventilation of neonatal lambs (0.005-0.02 l/sec). The slope of airway resistance (Raw)-flow curves and absolute values of Raw for the 3 PFC liquids were higher for the 3.0 ETT compared to the 4.0 ETT. The 3.0 ETT demonstrated resistance changes that were dependent on flow, density and viscosity. The 4.0 ETT showed a resistance-flow relationship that was relatively less dependent on flow, density and viscosity.
Assuntos
Resistência das Vias Respiratórias/efeitos dos fármacos , Fluorocarbonos/farmacologia , Intubação Intratraqueal/métodos , Animais , Animais Recém-Nascidos , Fenômenos Químicos , Físico-Química , Intubação Intratraqueal/instrumentação , OvinosRESUMO
To compare the effects of intermittent and continuous feedings on pulmonary function, we studied 24 very low birth weight neonates (mean +/- SD: birth weight, 1.2 +/- 0.3 kg; gestational age, 30.5 +/- 1.1 weeks) at 2 to 4 weeks of age. All infants had a previous diagnosis of respiratory distress syndrome but no subsequent diagnosis of bronchopulmonary dysplasia. Pulmonary mechanics were measured before the beginning of intermittent or continuous feedings and 10 minutes after each meal was completed. Twelve infants were randomly assigned to intermittent and 12 to continuous feedings. These infants had similar birth weight, gestational age, study age, and baseline lung function. After intermittent feedings, there was a significant decrease in tidal volume (38%), minute ventilation (44%), and dynamic compliance (28%), whereas pulmonary resistance increased significantly (100%). In comparison, the pulmonary function data remained unchanged after continuous feedings. These data demonstrate that intermittent feeding of very low birth weight infants can lead to airflow and respiratory instability. These adverse effects appear to be dependent on the rate that feedings are administered. A slower pace of feeding may be more advantageous for infants prone to respiratory instability.
Assuntos
Nutrição Enteral/métodos , Recém-Nascido de Baixo Peso/fisiologia , Mecânica Respiratória , Humanos , Recém-Nascido , Curvas de Fluxo-Volume Expiratório Máximo , Síndrome do Desconforto Respiratório do Recém-Nascido/fisiopatologia , Volume de Ventilação PulmonarRESUMO
High frequency jet ventilation (HFJV) was used to treat 176 infants who were either failing to respond to conventional mechanical ventilation (CMV) or demonstrating pulmonary air leak. The median birthweight for infants treated with HFJV was 1530 g, median gestational age was 31 weeks. Median duration of therapy with HFJV was 3.0, with a range of 0.1 to 27 days. During the first 24 hours of treatment, mean airway pressure decreased from 16.2 +/- 0.3 (Mean +/- SEM) cmH2O to 12.2 +/- 0.3 cmH2O, while mean PaO2 increased from 65.3 +/- 3.0 torr to 93.3 +/- 3.0 torr during the same time period. Simultaneously, mean PaCO2 decreased from 46.4 +/- 1.5 torr to 36.6 +/- 1.0 torr, although peak inflating pressure decreased from 34.3 +/- 0.7 cmH2O to 30.1 +/- 0.8 cmH2O. Ninety-five (54%) infants treated with HFJV survived. Of 123 infants with RDS 75 (61%) survived. The rate of complications for HFJV patients was similar to that seen with CMV in our nursery. This study suggests that HFJV provides improved oxygenation and ventilation of infants at lower mean and peak pressures compared to conventional mechanical ventilation. HFJV combined with CMV may be a valuable adjunct to therapy in infants with severe lung disease.
Assuntos
Ventilação em Jatos de Alta Frequência , Pneumopatias/terapia , Respiração Artificial , Doença Aguda , Terapia Combinada , Humanos , Recém-Nascido , Síndrome do Desconforto Respiratório do Recém-Nascido/terapia , Insuficiência Respiratória/terapiaRESUMO
Techniques for using the triploid cell marker for studying cell lineage during the development and regeneration of the axolotl limb are described. Triploid animals possess cells with three nucleoli while diploid animals possess cells with two nucleoli. We have developed a technique for isolating the limb dermis as a sheet of cells for whole-mount analysis of cellular ploidy. Whole-mount tissue preparations as well as paraffin-embedded sectioned tissues were stained specifically for nucleoli with bismuth. Cell counts from a number of triploid and diploid dermal preparations show that (1) diploid dermal cells never possess three nucleoli, (2) the frequency of trinucleolate cells in whole-mount triploid dermal preparations is not 100% but varies between animals from 30 to 76%, (3) within a single triploid animal, the frequency of trinucleolate cells in different dermal preparations is constant. These data establish the usefulness of this technique and emphasize the need for appropriate control cell counts when using the triploid cell marker in the axolotl.
Assuntos
Ambystoma mexicanum/fisiologia , Ambystoma/fisiologia , Pele/citologia , Animais , Extremidades/fisiologia , Ploidias , Regeneração , Coloração e RotulagemRESUMO
Fifteen infants with a specific clinical history including awake apnea were evaluated and compared with a control group of infants, using 24-hour studies of esophageal pH, nasal thermistor, impedance pneumography, and heart rate. Thirteen of the 15 children with awake apnea had clearly documented episodes of airway obstruction in associated with gastroesophageal reflux occurring at least twice during the study (mean 3.9 +/- 0.7, range 2 to 9). The control group did not show similar findings. All 15 children with awake apnea had frequent episodes of gastroesophageal reflux. Treatment with home monitoring and reflux precautions was successful in 10 of 15. Five children received therapy with urecholine hydrochloride because of continuing episodes of reflux-associated apnea. Two children subsequently required Nissen fundoplication, primarily for symptoms of severe esophagitis. Our data suggest that in children with awake apnea, the apnea is associated with gastroesophageal reflux. Medical management is usually successful, but fundoplication may be needed in refractory cases.
Assuntos
Apneia/complicações , Refluxo Gastroesofágico/complicações , Apneia/diagnóstico , Cardiografia de Impedância , Esôfago/fisiopatologia , Feminino , Refluxo Gastroesofágico/diagnóstico , Frequência Cardíaca , Humanos , Concentração de Íons de Hidrogênio , Lactente , Masculino , Pressão , SíndromeRESUMO
PPHN should be recognized as a clinical condition associated with a number of pulmonary and systemic diseases. Present therapy has resulted in increased survival, but the aggressive methods required to produce improvement necessitate a clear understanding of the underlying pathophysiology in order to minimize sequelae.
Assuntos
Síndrome da Persistência do Padrão de Circulação Fetal/diagnóstico , Cateterismo Cardíaco , Terapia Combinada , Diagnóstico Diferencial , Ecocardiografia , Cardiopatias Congênitas/diagnóstico , Humanos , Hiperventilação/diagnóstico , Recém-Nascido , Oxigênio/sangue , Síndrome da Persistência do Padrão de Circulação Fetal/fisiopatologia , Síndrome da Persistência do Padrão de Circulação Fetal/terapia , Prognóstico , Respiração Artificial , Vasodilatadores/uso terapêuticoAssuntos
Aminofilina/uso terapêutico , Ventilação com Pressão Positiva Intermitente/métodos , Respiração com Pressão Positiva/métodos , Síndrome do Desconforto Respiratório do Recém-Nascido/tratamento farmacológico , Humanos , Recém-Nascido , Síndrome do Desconforto Respiratório do Recém-Nascido/diagnóstico , Síndrome do Desconforto Respiratório do Recém-Nascido/terapiaRESUMO
To evaluate the relationship between improvement in pulmonary function and spontaneous diuresis in respiratory distress syndrome, nine premature infants requiring mechanical ventilation for RDS were studied at a mean age of 11.9 hours prior to the onset of diuresis, at onset of diuresis, at maximum urine output (mean age 44.9 hours), and at 24 hours after maximum urine output. Prior to diuresis functional residual capacity decreased from mean +/- SEM of 16.2 +/- 2 to 13.3 +/- 1.2 ml/kg, and dynamic lung compliance decreased from 2.5 +/- 0.3 to 1.8 +/- 0.3 ml/cm H2O (P less than 0.05), indicating that the respiratory disease was worsening. There was no significant change in alveolar-arterial oxygen gradient, peak inflating pressure, or rate of intermittent mandatory ventilation over this period. At the time of maximum urine output, however, FRC had increased 36% (P less than 0.05). CL had increased by 60% to 2.8 +/- 0.4 ml/cm H2O (P less than 0.025), AaDO2 had decreased from 246 +/- 27 to 184 +/- 30 torr (P less than 0.005), and PIP had decreased from 14.9 +/- 2.2 to 11.3 +/- 2.1 cm/H2O (P less than 0.05). On follow-up study 24 hours after maximum urine output, there was no further significant improvement in FRC, CL or PIP, but IMV rate and AaDO2 continued to decrease. These data show that the pulmonary function in RDS deteriorates until the onset of diuresis, after which it rapidly improves. This diuresis may represent the removal of excess lung liquid and seems necessary for improvement in RDS.
Assuntos
Diurese , Pulmão/fisiopatologia , Síndrome do Desconforto Respiratório do Recém-Nascido/terapia , Feminino , Hidratação , Humanos , Recém-Nascido , Medidas de Volume Pulmonar , Masculino , Respiração Artificial , Síndrome do Desconforto Respiratório do Recém-Nascido/urina , Testes de Função RespiratóriaRESUMO
To study the effects of two different heat shields commonly used under radiant warmers (thin plastic blanket vs a plastic body hood) on premature newborn infants, eight neonates were studied to measure insensible water loss and radiant power density at the skin under control and two shielded conditions. The body hood was found to diminish transmission of radiant heat to the infant's skin by 80%, absorbing heat and becoming warm (P less than 0.001). The plastic blanket absorbed only 15% of radiant warmer heat output (P less than 0.01). Insensible water loss was significantly less under the plastic blanket (1.88 +/- 0.4) ml/kg/hour) than under control (2.70 +/- 0.50 ml/kg/hour, P less than 0.01) and hood (2.86 +/- 0.32 ml/kg/hour, P less than 0.05) conditions. There was no decrease in insensible water loss under the hood compared to controls. This study demonstrates that a thin plastic blanket is the more effective shield against insensible water loss under a radiant warmer. Caution should be exercised with any shielding device to prevent interference with radiant heat delivery.
Assuntos
Temperatura Alta , Cuidado do Lactente , Recém-Nascido Prematuro , Temperatura Cutânea , Perda Insensível de Água/efeitos da radiação , Humanos , Recém-NascidoRESUMO
Ten premature infants nursed on servocontrolled radiant warmer beds were studied in three environments designed to alter one or more factors affecting heat transfer (convection, evaporation, and radiation). In the control environment, infants were nursed supine on an open warmer bed. The second environment (walled chamber) was designed to reduce convection and evaporation by placing plastic walls circumferentially around the bed. In the third environment convection and evaporation were minimized by covering infants with a plastic blanket. Air turbulence, insensible water loss, and radiant warmer power were measured in each environment. There was a significant reduction in mean air velocity in the walled chamber and under the plastic blanket when compared to the control environment. A parallel decrease in insensible water loss occurred. In contrast, radiant power demand was the same for control and walled environments, but decreased significantly when infants were covered by the plastic blanket. This study suggests that convection is an important factor influencing evaporation in neonates nursed under radiant warmers. The thin plastic blanket was the most effective shield, significantly reducing radiant power demand.
Assuntos
Leitos , Regulação da Temperatura Corporal , Ambiente Controlado , Incubadoras para Lactentes , Recém-Nascido Prematuro , Roupas de Cama, Mesa e Banho , Regulação da Temperatura Corporal/efeitos da radiação , Calefação , Humanos , Umidade , Recém-Nascido , Fenômenos Físicos , Física , Radiação , Temperatura Cutânea , Temperatura , Perda Insensível de Água/efeitos da radiaçãoRESUMO
To determine the relationship between improvement in pulmonary function and diuresis in respiratory distress syndrome, ten consecutive premature infants requiring mechanical ventilation for severe RDS were studied. Every infant had a diuresis (output/intake greater than 80%), which began at 26 to 34 hours of life and which lasted for an additional 64-72 hours. The diuresis preceded significant improvement in AaDo2 and ventilator settings (IMV, PIP, PEEP) by 52 hours. There was a significant decrease in body weight among all study infants during the first four days of life despite an increase in fluid intake. This study suggests a relationship in RDS between improvement in oxygenation and removal of interstitial lung edema.
Assuntos
Diurese , Respiração Artificial , Síndrome do Desconforto Respiratório do Recém-Nascido/fisiopatologia , Peso Corporal , Humanos , Recém-Nascido , Síndrome do Desconforto Respiratório do Recém-Nascido/terapia , Fatores de TempoRESUMO
To investigate the acute physiologic effects of external expiratory resistance on lung function in extubated neonates recovering from respiratory disease, lung mechanics, respiratory patterns, and functional residual capacity were measured in ten neonates dueing a control period and immediately after application of an external expiratory resistance of 30 cm H2O/l/second via a face mask. Following application of EER, mean FRC increased by 40.8% (P less than 0.05). The work of breathing was significantly increased after the EER was applied; there was also a significant increase in measured expiratory resistance and a decrease in inspiratory-expiratory time ratio. The change in lung volume was rapid, requiring less than five seconds for the new end-expiratory level to be reached. Dynamic lung compliance, inspiratory resistance, and respiratory rate did not change during any phase of the study. The application of external expiratory resistance may have potential therapeutic value by increasing lung volume in infants recovering from respiratory disease.
Assuntos
Doenças do Recém-Nascido/fisiopatologia , Respiração com Pressão Positiva , Doenças Respiratórias/fisiopatologia , Resistência das Vias Respiratórias , Fluxo Expiratório Forçado , Capacidade Residual Funcional , Humanos , Recém-Nascido , Intubação Intratraqueal/efeitos adversos , Complacência Pulmonar , Medidas de Volume Pulmonar , Respiração , Doenças Respiratórias/terapia , Trabalho RespiratórioRESUMO
Fourteen intubated infants recovering from neonatal respiratory disease had arterial blood gases and lung mechanics measured in the supine position and in two variants of the prone position. Prone positioning resulted in significant increases in mean (+/- SEM) arterial oxygen tension (Pa(o2 70.4 +/- 2.5 to 81.1 +/- 4.4mm Hg), dynamic lung compliance (1.7 +/- 0.24 to 2.55 +/- 0.37 ml/cm H2O),and tidal volume (8.6 +/- 1.0 to 10.5 +/- 1.2 ml) when all prone values were compared to supine values. Prone positioning with the abdomen protruding freely, when compared to all supine values, was associated with significantly increased dynamic lung compliance and tidal volume. Values for prone-abdomen free were not significantly different from values for prone-abdomen restricted. This suggests that there are clinical benefits from prone positioning in neonates recovering from respiratory disease.